/* Refer to:
 * http://android-developers.blogspot.com/2010/07/multithreading-for-performance.html
 */
package edu.cmu.ece.ds.droidchat.util;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.net.MalformedURLException;
import java.net.URL;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.content.Context;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.Log;
import android.widget.ImageView;
import edu.cmu.ece.ds.droidchat.R;
import edu.cmu.ece.ds.droidchat.model.UserInfo;
import edu.cmu.ece.ds.droidchat.view.LoggedInUserView;

public class ImageDownloader {

    private static final String TAG = "ImageDownloader";

    public void downloadToLoggedInUserInfoView(UserInfo myInfo,
            LoggedInUserView view) {
        download(myInfo, view.getUserIconView());
    }

    public void downloadToUserInfo(String url, UserInfo uInfo,
            ImageView imageView) {
        if (cancelPotentialDownload(url, imageView)) {
            DrawableDownloaderTask task = new DrawableDownloaderTask(uInfo,
                    imageView);
            DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task, imageView.getContext());
            imageView.setImageDrawable(downloadedDrawable);
            task.execute(url);
        }
    }

    public void download(String url, ImageView imageView) {
        downloadToUserInfo(url, null, imageView);
    }

    public void download(UserInfo uInfo, ImageView imageView) {
        downloadToUserInfo(uInfo.getProfilePictureURLString(), uInfo, imageView);
    }

    private static boolean cancelPotentialDownload(String url,
            ImageView imageView) {
        DrawableDownloaderTask bitmapDownloaderTask = getDrawableDownloaderTask(imageView);

        if (bitmapDownloaderTask != null) {
            String bitmapUrl = bitmapDownloaderTask.url;
            if ((bitmapUrl == null) || (!bitmapUrl.equals(url))) {
                bitmapDownloaderTask.cancel(true);
            } else {
                // The same URL is already being downloaded.
                return false;
            }
        }
        return true;
    }

    private static DrawableDownloaderTask getDrawableDownloaderTask(
            ImageView imageView) {
        if (imageView != null) {
            Drawable drawable = imageView.getDrawable();
            if (drawable instanceof DownloadedDrawable) {
                DownloadedDrawable downloadedDrawable = (DownloadedDrawable) drawable;
                return downloadedDrawable.getBitmapDownloaderTask();
            }
        }
        return null;
    }

    static Drawable downloadDrawable(String url) {
        try {
            // Well, seems there's a bug in Drawable.createFromStream().
            // refer to
            // http://groups.google.com/group/android-developers/browse_thread/thread/4ed17d7e48899b26/
            InputStream is = new URL(url).openStream();
            Drawable d = Drawable.createFromStream(new FlushedInputStream(is),
                    "src name");
            is.close();
            return d;
        } catch (IOException e) {
            Log.e(TAG, "LoadFacebookProfileImage error.");
            return null;
        }
    }

    private static InputStream fetch(String urlString)
            throws MalformedURLException, IOException {
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpGet request = new HttpGet(urlString);
        HttpResponse response = httpClient.execute(request);
        return response.getEntity().getContent();
    }

    class DrawableDownloaderTask extends AsyncTaskExt<String, Void, Drawable> {
        private String url;
        private final WeakReference<ImageView> imageViewReference;
        private final WeakReference<UserInfo> userInfoReference;

        public DrawableDownloaderTask(UserInfo uInfo, ImageView imageView) {
            imageViewReference = new WeakReference<ImageView>(imageView);
            // uInfo can be null.
            userInfoReference = new WeakReference<UserInfo>(uInfo);
        }

        @Override
        // Actual download method, run in the task thread
        protected Drawable doInBackground(String... params) {
            // params comes from the execute() call: params[0] is the url.
            return downloadDrawable(params[0]);
        }

        @Override
        // Once the image is downloaded, associates it to the imageView
        protected void onPostExecute(Drawable d) {
            if (isCancelled()) {
                d = null;
            }

            if (imageViewReference != null) {
                ImageView imageView = imageViewReference.get();
                UserInfo uInfo = userInfoReference.get();
                DrawableDownloaderTask bitmapDownloaderTask = getDrawableDownloaderTask(imageView);
                // Change bitmap only if this process is still associated with
                // it
                if (this == bitmapDownloaderTask) {
                    imageView.setImageDrawable(d);
                    if (uInfo != null) {
                        uInfo.setProfilePicture(d);
                    }
                }
            }
        }
    }

    static class DownloadedDrawable extends BitmapDrawable {
        private final WeakReference<DrawableDownloaderTask> drawableDownloaderTaskReference;

        public DownloadedDrawable(DrawableDownloaderTask drawableDownloaderTask, Context context) {
            super(context.getResources(),BitmapFactory.decodeResource(context.getResources(), R.drawable.no_picture));
            drawableDownloaderTaskReference = new WeakReference<DrawableDownloaderTask>(
                    drawableDownloaderTask);
        }

        public DrawableDownloaderTask getBitmapDownloaderTask() {
            return drawableDownloaderTaskReference.get();
        }
    }

    static class FlushedInputStream extends FilterInputStream {
        public FlushedInputStream(InputStream inputStream) {
            super(inputStream);
        }

        @Override
        public long skip(long n) throws IOException {
            long totalBytesSkipped = 0L;
            while (totalBytesSkipped < n) {
                long bytesSkipped = in.skip(n - totalBytesSkipped);
                if (bytesSkipped == 0L) {
                    int b = read();
                    if (b < 0) {
                        break; // we reached EOF
                    } else {
                        bytesSkipped = 1; // we read one byte
                    }
                }
                totalBytesSkipped += bytesSkipped;
            }
            return totalBytesSkipped;
        }
    }
}
